P and D made a contract for towage. P's barge had no motive power, steering apparatus, officers, or crew. Its movements were completely controlled by D. The contract provided that the towing movement should be at the 'sole risk' of the barge and that masters, crews, and employees of the towboat should 'in the performance of said service, become and be the servants' of P. D’s towboat performed so well that P’s barge hit a bridge pier and sank. P sued D and D claimed the contract and all of its provisions were valid and enforceable. The District Court, sitting in admiralty, sustained the contractual provision exempting D from liability for negligence and entered judgment accordingly. The Court of Appeals affirmed. P appealed.